Piezoelectric materials, such as crystals, ceramics, formulations of lead, magnesium, and niobate (PMN), formulations of lead, zirconate, and titanate (PZT), or the like, produce a stress and/or strain when an electric field is applied thereto. As such, piezoelectric materials are often used as actuators for imparting forces to materials or objects that they are in contact with. For example, piezoelectric materials are often used to impart forces to deflect materials they are in contact with.
In one example, one or more piezoelectric actuators may form part of a fluid-ejection device, such as a print-head. For this implementation, piezoelectric actuators are formed overlying a deflectable-layer, e.g., a conductive layer, such as a ground layer, overlying a glass-layer. The deflectable-layer is formed overlying a semiconductor substrate, e.g., of silicon, having channels, such as ink-delivery channels, formed therein such that a piezoelectric actuator corresponds to each channel. During operation, a selected actuator imparts a force to the deflectable-layer in response to an electric field being applied to the actuator. The force imparted to the deflectable-layer deflects the deflectable-layer, causing a drop of fluid, such as ink, to be ejected from the channel corresponding to the selected actuator.
In conventional fabrication methods, the piezoelectric actuators are typically formed by using an adhesive to bond a layer of piezoelectric material to the deflectable-layer. The layer of piezoelectric material is then cut into segments, e.g., using a saw or other similar mechanical cutting tool, so that each segment forms a piezoelectric actuator. To avoid destroying the deflectable-layer by contacting the deflectable-layer with the saw, the depth of each saw cut extends to within a certain distance, e.g., about 5 to about 15 microns, from the deflectable-layer. However, this can leave piezoelectric material and adhesive at the end of each saw cut that extends between neighboring actuators.
The piezoelectric material that extends between neighboring actuators can produce cross-talk between the neighboring actuators. For example, when an electric field is applied to one of the actuators, the neighboring actuators may also respond. This can adversely affect the timing and the impact velocity of the ejected drops, which can adversely affect print quality.
Another problem associated with leaving piezoelectric material and adhesive at the end of each saw cut is that the piezoelectric material and adhesive acts to reduce the compliance of the deflectable-layer. Therefore, the electric field applied to the actuators may need to be increased to properly deflect the deflectable-layer. However, increased electric fields act to increase degradation of piezoelectric materials and thus acts to reduce the life of the actuators.